stem cell

stem cell

2. a cell with daughter cells that may differentiate into other cell types.

3. a cell capable of maintaining its own number while exporting progeny to one or more cell lineages.

stem cell

n.

An unspecialized cell that can give rise to one or more different types of specialized cells, such as blood cells and nerve cells. Stem cells are present in embryos and in various tissues of adult organisms and are widely used in scientific research.

stem cell

Etymology: AS, stemm, tree, trunk; L, cella, storeroom

a formative cell; a cell whose daughter cells may give rise to other cell types. A pluripotential stem cell is one that has the potential to develop into several different types of mature cells, including lymphocytes, granulocytes, thrombocytes, and erythrocytes. See also hematopoietic stem cell.

stem cell

(stem sel)

1. Any precursor cell.

2. A cell with daughter cells that may differentiate into other cell types.

stem cell

a special kind of cell from an EMBRYO, FOETUS or adult, capable of renewing itself under certain conditions, and of becoming specialized cells that make up the different TISSUES and ORGANS of the body A stem cell remains largely undifferentiated and uncommitted to a specific function, until it receives a signal to develop into a specialized cell (see CELL DIFFERENTIATION). An embryonic stem cell derives from a group of cells, the inner cell mass, from a 4–5 day old embryo, called a BLASTOCYST. This group of cells can be removed and cultured into embryonic stem cells. An embryonic germ cell derives from foetal cells destined to be reproductive cells (see GERM LINE). Embryonic stem cells and germ cells have the potential to differentiate into almost any or all of the cell types of the body i.e. they are ‘pluripotent’, but they do not have identical properties. An adult stem cell is an undifferentiated cell occurring in differentiated tissue, such as that of BONE MARROW, BRAIN, SKELETAL MUSCLE, LIVER, SKIN, PANCREAS or the BLOOD, with the capacity to yield specialized cell types of the tissue of origin. However, adult stem cells appear to have the potential to generate specialized cells of another tissue under appropriate conditions, for example cells from bone marrow generating cells resembling NEURONS and other cell types found in the brain. Hence it seems that they are capable of being genetically reprogrammed. The ability of stem cells to proliferate and to differentiate into specialized cell types makes them potentially useful for the repair and replacement of damaged and diseased tissues, see THERAPEUTIC CLONING.

Stem cell

Undifferentiated cell that retains the ability to develop into any one of numerous cell types.

stem cell

(stem sel)

1. Any precursor cell.

2. Cell with daughter cells that may differentiate into other cell types.

cell

1. the basic structural unit of living organisms.

2. a small more or less enclosed space.

All living cells arise from other cells, either by division of one cell to make two, as in mitosis and meiosis, or by fusion of two cells to make one, as in the union of the sperm and ovum to make the zygote in sexual reproduction.

All cells are bounded by a structure called the cell membrane or plasma membrane, which is a lipid bilayer composed of two layers of phospholipids. Each layer is one molecule thick with the charged, hydrophilic end of the lipid molecules on the surface of the membrane and the uncharged hydrophobic fatty acid tails in the interior of the membrane.

Cells are divided into two classes, eukaryotic cells and prokaryotic cells:

Eukaryotic cells have a true nucleus, which contains the genetic material, composed of the chromosomes, each of which is a long linear deoxyribonucleic acid (DNA) molecule associated with protein. The nucleus is bounded by a nuclear membrane, which is composed of two lipid bilayer membranes.

Prokaryotic cells, the bacteria, have no nucleus, and their genetic material, consisting of a single circular naked DNA molecule, is not separated from the rest of the cell by a nuclear membrane.

Eukaryotic cells are larger and more complex than prokaryotic cells. They also have membrane-bounded structures, such as mitochondria, chloroplasts, Golgi apparatus, endoplasmic reticulum and lysosomes, that prokaryotic cells lack.

The contents of a cell are referred to collectively as the protoplasm. In eukaryotic cells the contents of the nucleus are referred to as nucleoplasm and the rest of the protoplasm as the cytoplasm.

The lipid bilayer of eukaryotic cells is impermeable to many substances, such as ions, sugars and amino acids; however, membrane proteins selectively move specific substances through the cell membrane by active or passive transport. Water, gases such as oxygen and carbon dioxide, and nonpolar compounds pass through the cell membrane by diffusion. Materials can also be engulfed and taken into the cell enclosed in a portion of the cell membrane. This is called phagocytosis when solids are ingested and pinocytosis when liquids are ingested. The reverse process is called exocytosis. All of these processes permit the cell to maintain an internal environment different from its exterior. See also body fluids.

The cells of the body differentiate during development into many specialized types with specific tasks to perform. Cells are organized into tissues and tissues into organs. Embedded in the cell membrane are a wide range of molecules that vary with the cell type and are typically composed of proteins or glycoproteins that have a cytoplasmic transmembrane and external domains. These molecules serve as cell receptors and are involved in signal transduction for a wide range of ligands, including hormones, cytokines and incidentally serve as receptors for viruses and drugs.

enterochromaffin cells containing cytoplasmic granules capable of reducing silver compounds, located throughout the gastrointestinal tract, chiefly in the basilar portions of the gastric glands and the crypts of Lieberkühn. They secrete serotonin.

band cell

an immature neutrophil in which the nucleus is not lobulated but is in the form of a continuous band, horseshoe shaped, twisted or coiled. Called also band-form granulocyte and stab cell.

basal cell

an early keratinocyte, present in the basal layer of the epidermis.

basket c's

cells in the cerebellar cortex whose axons carry basket-like groups of fibrils which enclose the cell body of each Purkinje cell.

beta c's

1. basophilic cells in the pancreas that secrete insulin and make up most of the bulk of the islets of Langerhans; they contain granules that are soluble in alcohol.

a very large, multinucleate cell; applied to megakaryocytes of bone marrow, to giant cells formed by coalescence and fusion of macrophages occurring in infectious granulomas and about foreign bodies, and to certain cancer cells.

glial c's

neuroglial cells.

goblet cell

a unicellular mucous gland found in the epithelium of various mucous membranes, especially that of the respiratory passages and intestines.

granular cell

one containing granules, such as a keratinocyte in the stratum granulosum of the epidermis, when it contains a dense collection of darkly staining granules.

iron-containing, rust-colored macrophages found in the pulmonary alveoli in congestive heart failure.

helmet cell

schistocyte.

helper cell

a subset of T lymphocytes which cooperate with B and other T lymphocytes for the synthesis of antibodies to many antigens; they play an integral role in immunoregulation.

hybrid cell

a mononucleate cell produced from a binucleate heterokaryon after the latter undergoes mitosis. Such cells are initially unstable, tending to lose randomly some of the double complement of chromosomes. Used for mapping genes to particular chromosomes. See also heterokaryon, hybridoma.

the cells of the connective tissue of the ovary or of the testis (Leydig's cells) which furnish the internal secretion of those structures, i.e. testosterone.

islet c's

cells composing the islets of Langerhans in the pancreas. See alpha cells, beta cells (above).

juxtaglomerular c's

specialized cells, containing secretory granules, located in the tunica media of the afferent glomerular arterioles. They cause aldosterone production by secreting the enzyme renin and play a role in the regulation of blood pressure and fluid balance.

lymphocyte-like cells that lack specific antigen receptors and other surface markers characteristic of B and T lymphocytes; they include K and NK cells; their numbers are elevated in active systemic lupus erythematosus and other disease states.

olfactory c's

a set of specialized cells of the mucous membrane of the nose; the receptors for smell.

round, oval or polyhedral cells with foamy, lipid-containing cytoplasm found in the bone marrow and spleen in Niemann-Pick disease.

plasma cell

a spherical or ellipsoidal cell with a single, eccentrically placed nucleus containing dense masses of chromatin in a wheel-spoke arrangement, an area of perinuclear clearing which contains the Golgi apparatus, and generally abundant cytoplasm. Plasma cells are produced by cell division of B lymphocytes following antigen stimulation and are involved in the synthesis and release of antibody. Called also plasmacyte and plasmocyte.

prickle cell

a dividing keratinocyte of the prickle-cell layer of the epidermis, with delicate radiating process connecting with other similar cells.

giant histiocytic cells, typically multinucleate, which are the common histological characteristic of Hodgkin's disease in humans.

reticular c's

the cells forming the reticular fibers of connective tissue; those forming the framework of lymph nodes, bone marrow and spleen. They are weakly phagocytic, stromal in origin and are distinct from the monocyte-macrophage system.

any of the large nucleated cells whose cell membrane spirally enwraps the axons of myelinated peripheral neurons supplying the myelin sheath between two nodes of Ranvier.

Sertoli c's

elongated cells in the tubules of the testes to which the spermatids become attached; they provide support, protection and, apparently, nutrition until the spermatids are transformed into mature spermatozoa.

sickle cell

a crescentic or sickle-shaped erythrocyte seen in some humans and deer. The abnormal shape caused by the presence of varying proportions of hemoglobin S.

signet-ring cell

a cell in which the nucleus has been pressed to one side by an accumulation of intracytoplasmic mucin.

conversion of a simple cell type into a specialized cell type capable of a special function, e.g. a secretory cell; a major part of the growth of an embryo and the differentiation of basic mesenchymal tissue into specialized organs.

any star-shaped cell, as a Kupffer cell or astrocyte, having many filaments extending in all directions.

stem cell

1. any precursor cell.

2. a primitive hematopoietic cell that is capable of self-replicating or differentiating into precursor cells of erythrocytes or any of the leukocytes.

stipple cell

an erythrocyte containing granules that take a basic or bluish stain with Wright's stain.

suppressor c's

a not well defined subset of T lymphocytes that are reported to inhibit antibody and cell-mediated immune responses. They may play a role in immunoregulation, and are believed to be abnormal in various autoimmune and other immunological disease states. See also T lymphocytes.

target cell

1. an abnormally thin erythrocyte showing, when stained, a dark center and a peripheral ring of hemoglobin, separated by a pale, unstained zone containing less hemoglobin; seen in various anemias and other disorders. Called also codocyte.

2. any cell selectively affected by a particular agent, such as a hormone or drug.

3. cell containing nonself antigens in its cell membranes that is a target for nonimmune and immune cytolysis, e.g. virus-infected or tumor cell.

taste c's

cells in the taste buds associated with the nerves of taste.

cell therapy

see glandular therapy.

totipotential cell

an embryonic cell that is capable of developing into any type of body cell.

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